轻度认知功能损害诊断:脑血管病因素对神经心理学指标的影响

目的对神经心理学指标在轻度认知功能损害(MCI)诊断中的作用进行评价;了解脑血管病因素对MCI诊断标准的 影响。方法从老年人流行病学凋查人群中随机抽取78人为研究对象,设正常对照组(41人)及MCI组(37例)。 对2组进行以下 观测:简易精神状态检查(MMSE)、总体衰退量表(GDS)、临床痴呆分级量表(CDR)、日常生活能力(ADL)、Pfeffer功能活动量表 (FAQ)、物体记忆测验(FOM)、无意义图形再认(MGR)、词语流畅性测验(RVR)、数字广度测验(DS)、画钟测验(CDT)、流调用抑郁 自评量表(CES—D)、延迟记忆(DR)及逻辑记忆测验(LM)。结果MCI组的FOM、MGR、LM、MMSE、DR、FAQ、CDT、CDR、GDS等测 验成绩明显差于正常对照组。在排除了脑血管病之后,MCI组的MGR、FOM、LM、CDT、DR、CDR、GDS等测验分数仍明显差于正常对 照组,但MMSF、FAQ测验在2组之间的差别不再具有统计学意义。结论脑血管病因素对MCI诊断的某些神经心理学指标有影响: MCI存在异质性,部分可以由脑血管病造成。在诊断MCI时,应该增加排除标准。     

轻度认知功能障碍患者情绪记忆损害特征

目的探讨轻度认知功能障碍(MCI)患者情绪记忆的改变。方法采用情绪记忆神经认知心理学检查评价22例MCI患者(MCI组)及22名健康成年人(正常对照组)的情绪记忆,并采用事件诱发电位(ERPs)检测P300的潜伏期和波幅。结果与正常对照组比较,MCI组MMSE、词汇流畅性试验、数字广度试验评分均显著降低(均P 0. 01)。MCI组与正常对照组正性、中性和负性情绪图片效价度差异无统计学意义(均P 0. 05)。与正常对照组比较,MCI组正性和负性图片再认正确率均显著降低(P 0. 05～0. 01),中性图片再认正确率差异无统计学意义(P 0. 05)。MCI组及正常对照组正性、负性与中性图片再认正确率差异有统计学意义(F=6. 27,F=39. 13;均P 0. 05)。与正常对照组比较,MCI组正性和负性图片再认反应时间差异有统计学意义(P 0. 05～0. 01),中性图片差异无统计学意义(P 0. 05)。MCI组及正常对照组正性、负性与中性图片再认反应时间差异有统计学意义(F=3. 74,F=16. 48;均P 0. 05)。MCI组与正常对照组学习阶段ERPs-P300的潜伏期、波幅差异无统计学意义(均P 0. 05)。与正常对照组比较,MCI组再认阶段正性和负性图片ERPs-P300潜伏期显著增加,波幅显著降低(P 0. 05～0. 01);中性图片潜伏期及波幅差异无统计学意义(均P 0. 05)。MCI组学习阶段(F=55. 20,P 0. 05; F=43. 12,P 0. 05)及再认阶段(F=29. 36,P 0. 05; F=19. 39,P 0. 05)正性、负性与中性情绪图片ERPs-P300潜伏期及波幅差异均有统计学意义;正性与负性ERPs-P300潜伏期及波幅比较差异无统计学意义(均P 0. 05)。正常对照组的学习阶段(F=55. 66,P 0. 05; F=39. 33,P 0. 05)及再认阶段(F=114. 48,P 0. 05; F=51. 77,P 0. 05)正性、负性与中性情绪图片ERPs-P300潜伏期及波幅差异均有统计学意义。结论 MCI患者存在情绪记忆的受损及反应时间延长,且情绪效价"正向"选择性偏向受损。     

扩瞳试验对阿尔茨海默病的预测效应

目的利用扩瞳试验对轻度认知功能损害(Mild cognitive impairment,MCI)患者进行研究,了解MCI、阿尔茨海默病(AD)与正常老年人在扩瞳试验结果之间的差异,分析MCI与AD之间的关系,并探讨扩瞳试验是否能作为MCI发展成AD的预测指标。方法收集AD患者30例、MCI患者28例以及健康对照34例。分别进行神经心理学测验和扩瞳试验。比较三组的神经心理学测验和扩瞳试验结果之间的差异。计算扩瞳试验在诊断AD和MCI时的敏感性和特异性。结果MCI组的神经心理学测验都显著好于AD组(P<0.001),但都明显不如正常对照组(P<0.001)。AD患者和MCI患者在滴入扩瞳剂后,瞳孔直径明显扩大,与NC组有显著差异(P值分别为P<0.05,P<0.001),而AD组与MCI组之间则无统计学上的差异(P>0.05)。扩瞳试验诊断AD的敏感性和特异性分别为60.0%和67.65%,诊断MCI的敏感性和特异性分别为71.43%和67.65%。结论扩瞳试验可以将MCI患者和AD患者、与正常老年人区别开来,可以作为MCI和AD的一个筛选诊断标志。MCI是AD与正常衰老之间的过渡状态;MCI患者是AD的高危人群...     

快速认知筛查测验在检测轻度认知损害中的应用研究(英文)

目的轻度认知损害(mild cognitive impairment,MCI)可根据认知表现分为遗忘型MCI(aMCI)和非遗忘型MCI(naMCI)。本研究旨在编制快速认知筛查测验(quick cognitive screening test,QCST)便于快速全面地识别MCI,为进一步研究提供依据。方法符合MCI操作性诊断标准的MCI组121例、符合DSM-Ⅳ有关痴呆诊断标准的阿尔茨海默病(AD)组79例和正常老年人组186例,参与了QCST和标准化全套神经心理测验。参与者教育程度均在5年或以上,年龄55-85岁。QCST项目包括即刻记忆、延迟回忆、命名、动物流畅性、相似性、彩色连线B、画钟、手指结构、数字广度等9个分测验,每个分测验满分10分,总分90分,耗时10-15分钟。结果MCI组、AD组和正常老年人组QCST总分分别为(58.13±8.18)、(44.53±10.54)和(72.92±6.85)分。制定教育程度在5-8年、9-12年、高于13年3个组别的QCST总分的划界分分别为63、65和68分。QCST识别MCI的敏感性为87.6%,其中识别aMCI-s、aMCI-m和naMCI的敏感性分别...     

轻度认知障碍患者情感记忆编码和提取受损的研究

目的探讨轻度认知障碍(MCI)患者情感记忆编码和提取受损的特点,为极早发现MCI和干预治疗前移评估提供理论依据.方法人选MCI组34例,选取30例健康老年人作为对照组,所有受试者均进行情感记忆编码和提取测试.结果MCI组情感图片记住数(REM)(21.32±7.29)%明显低于对照组(26.00±9.57)%(P＜0.05),MCI组情感图片靶片提取率(85.44±4.94)%与对照组(96.76±2.18)%比较有极显著差异(P＜0.01).MCI组IPreti与(PP+UP)reti比较无显著性差异(t=1.41,P＞0.05),对照组IPreti与(PP+UP)reti比较有显著性差异(t=15.24,P＜0.05).两组间IPreti比较无显著性(t=1.28,P＞0.05),(PP+UP)reti比较有极显著性差异((t=25.49,P＜0.01).PPreti (Pleasant pictures retrieval index)、Upreti(unpleasant pictures retrieval index)IPreti(indifferent picturesretrieval index).结论MCI患者存在情感记忆编码受损,载有情感内容的图片不能增强MCI患者情感记忆提取,情感记忆编码和提取测试为极早发现MCI有效工具之一.     

轻度认知功能障碍患者的神经心理学测试

目的探讨轻度认知功能障碍(MCI)患者是否有神经心理方面的损害及损害的特点,以期为早期筛查出MCI患者提供参考指标。方法采用数字颜色连线测验(CTT)、数字广度测试(DS)、词汇流畅性测试(VFT)、中文听觉词汇(CALT)、线段方向判断(JLOT)和Stroop测验对30名MCI患者和30名性别、年龄和教育程度相匹配的正常对照组进行评定。结果MCI患者的CTT、VFT、数字广度倒背和CALT与正常对照组相比差异均有显著性。JLOT、Stroop测验和数字广度顺背成绩虽有所下降,但差异均无显著性。结论MCI患者的神经心理方面有损害。对MCI危险人群进行神经心理学测试能早期筛选出MCI患者。     

轻度认知功能障碍患者认知功能与内颞叶各结构体积的关系

目的研究轻度认知功能障碍(MCI)患者认知功能与内颞叶各结构体积的关系。方法17例MCI患者和21名正常老年人分别接受临床评估、神经心理检查和头颅MR扫描,在重建的图像上测量内颞叶各结构的体积,并行标准化处理;对神经心理学指标与内颞叶结构MR指标进行相关性分析。结果MCI组和正常老年组的神经心理量表除物体记忆测验(FOM)外,其余各项得分差异均无统计学意义;两组MR内颞叶结构体积比较差异亦均无统计学意义(均P>0.05)。在MCI组中,短时记忆、逻辑记忆(LM)得分与内嗅皮质体积呈正相关(r=0.484、0.529,均P<0.05),无意义图形再认(MGR)、FOM得分与海马体积呈正相关(r=0.502、0.659,均P<0.05),短时记忆、MGR得分与左侧杏仁核体积呈正相关(r=0.557、0.644,均P<0.05);正常老年组短时记忆、LM和数字广度(DS)测验得分与双侧内嗅皮质体积呈负相关(r=-0.448、-0.718,均P<0.05),注意力、计算力与右侧杏仁核、双侧海马体积均呈负相关(r=-0.451、-0.553,均P<0.05)。结论MCI患者的认知功能与内颞叶各结构体积有关;不同的认知功...     

轻度认知功能障碍患者的神经心理学研究

目的 探讨轻度认知功能障碍(MCI)患者神经心理学的特点. 方法 对42例MCI患者和55例健康对照者进行多项神经心理学检查,包括简易精神状态检查量表(MMSE)、蒙特利尔认知评估量表(MoCA)、临床痴呆评定量表(CDR)、语言流畅性测验(RVR)、韦氏智力测验(WAIS-RC)[包括数字广度测验(DS)、积木测验(BD)、相似性测验]、韦氏记忆测验(WMS-R)(包括逻辑记忆、联想学习、视觉再认、图片回忆)、日常生活能力量表(ADL),比较2组患者上述量表评分和MMSE、MoCA量表各亚项评分的差异.结果 与对照者比较,MCI患者MMSE、MoCA总分和RVR、WAIS-RC、WMS-R分测验,MoCA量表各亚项(地点定向力除外),MMSE量表中计算与注意、延迟回忆两亚项评分较低,差异均有统计学意义(P<0.05).结论 MCI患者不仅记忆受损,其计算与注意力、命名、视空间结构能力、执行功能也可受损,尤以延迟回忆、计算与注意力受损明显.MoCA涵盖了重要的认知领域,能较全面评估MCI患者的认知功能,值的临床推广应用.     

轻度认知损害患者的空间结构能力障碍

目的 研究轻度认知损害(mild cognitive impairment,MCI)患者空间结构能力的缺损与保持状况.方法 将被试者分为3组:健康对照组122名,其中男51名、女71名;MCI组205例,男95例、女110例,其中遗忘型MCI(aMCI)133例,非遗忘型MCI(naMCI)72例;阿尔茨海默病(AD)组75例,男36例、女39例.全部进行Rey-Osterrieth复杂图形测验(CFT)、画钟测验(CDT)、搭火柴测验3个结构能力测验,同时完成简易精神状态量表(MMSE)等测验.健康对照组、MCI组和AD组MMSE平均得分分别为28.24±1.74、27.39±1.83和19.98±3.23.采用SPSS for windows 11.5统计软件,计数资料采用卡方检验,3组间比较采用One-way方差分析,然后采用Bonferroni(LSD)法进行多重比较.结果(1)以健康组为对照,CFT模仿得分和CDT总分与年龄、教育年限没有显著相关性,搭火柴测验-旋转部分(STR)与年龄有相关性(r=-0.179,P＜0.05),与教育年限没有显著相关性.(2)CFT模仿得分与CDT总分(r=0.337)、STR(r=0.232),CDT总分与STR(r =0.235),均有显著相关性(均P＜0.01).(3)CFr模仿和CDT总分分别与反映执行功能的连线测验B、Stroop色词测验卡片C耗时数的相关性最高,而STR与反映记忆的指标听觉词语学习测验的相关性高.CFT模仿、CDT总分和STR在健康对照组、MCI组和AD组之间差异有统计学意义.(4)在识别MCI方面,经过对3组结构测验表现的比较得出STR优于CFT模仿、CDT总分.结论 结构能力损害是MCI的表现之一,空间旋转能力的评估在识别MCI方面优于CFT模仿、CDT总分.     

Rey-Osterriche复杂图形测验在轻度阿尔茨海默病和轻度认知损害患者中的应用研究

目的:研究Rey-Osterrich复杂图形测验(CFT)对轻度阿尔茨海默病(AD)和遗忘型轻度认知损害(MCI)的诊断价值。方法:应用CFT、简明精神状态量表(MMSE)对45例轻度AD患者、73例遗忘型MCI和66名正常老年人进行检测,MMSE总得分分别为(20.2±2.5)分、(26.9±1.8)和(28.2±1.6)分。结果:对照组,CFT结构模仿和延迟回忆得分与教育程度有显著正相关性,与年龄、性别无相关性。MCI组的结构模仿得分为(32.4±6.2)分,轻度AD组为(26.1±10.9)分,对照组为(33.6±3.1)分。AD组与对照组及MCI组比差异有显著意义,延迟记忆对于识别MCI有一定作用,协助AD诊断有较好的敏感性(P<0.01);MCI组的延迟回忆得分与对照组比差异有显著统计学意义(P<0.01),轻度AD组下降更为明显,与MCI组比差异有显著统计学意义(P<0.01)。结论:CFT延迟记忆对于识别MCI有一定作用,协助AD诊断有较好的敏感性。CFT结构模仿不能识别MCI,对轻度AD,其敏感性亦不理想。     

Subtle memory decline over 12 months in mild cognitive impairment

OBJECTIVE: Screening of normal older persons for progressive memory decline is a worthwhile strategy in the pursuit of the earliest possible stages of pre-clinical Alzheimer's disease (AD) or mild cognitive impairment (MCI). Reliable tests are needed to both detect MCI and measure the natural history of decline over months rather than years. We aimed to detect memory decline over 1 year in a group of older individuals with well-characterised amnestic MCI. METHODS: The continuous learning task (CLT) from the CogState test battery was administered 8 times in 12 months to 15 individuals with MCI and 35 controls matched for age, education, IQ and gender. All subjects were recruited from an ongoing aging study. The rate of change in CLT performance over the year was compared between groups and also compared to that detected with a word list learning task and a computerised paired associate learning task. RESULTS: At baseline, memory performance in the amnestic MCI group was significantly worse than controls on all memory tests. However, at 12 months the magnitude of the difference between the groups had increased significantly on the CLT due to decline in memory accuracy in the MCI group. No decline over 12 months was detectable on the routine memory tests. CONCLUSIONS: Subtle memory decline is detectable in amnestic MCI using reliable and sensitive tests of memory. Such measures may assist in the early identification of AD and also in trials of putative disease-modifying therapies to be conducted over as little as 12 months.     

老年轻度认知障碍记忆损害特点的研究

目的探讨老年轻度认知障碍患者的记忆损害特点,比较不同神经心理学测验对诊断和发现轻度认知障碍的敏感性,筛选临床实用的简捷敏感的神经心理学测验工具。方法轻度认知障碍患者20例,轻度阿尔茨海默病患者26例,健康老年人30名。应用词语回忆测验、图片回忆测验、数字广度测验、本顿视觉保持测验C式A法及D式D法进行测试。结果轻度认知障碍组在图片回忆分、视觉保持测验D式D法正确分及持续错误分上的成绩较正常对照组差(P<0．05);轻度认知障碍组视觉保持测验D法成绩明显差于A法(P<0．01)。结论轻度认知障碍患者对具体视觉形象的记忆能力及对无意义图形的视觉记忆能力受损,存在即刻记忆和延迟记忆障碍,且延迟回忆较即刻回忆损害明显,短时记忆更新的可塑性差;图片回忆测试、本顿视觉保持测验的延迟回忆测试或与即刻回忆联合测试有助于轻度认知障碍的早期发现。     

Comparison between the story recall test and the word-list learning test in Korean patients with mild cognitive impairment and early stage of Alzheimer's disease

Among verbal memory tests, two that are commonly used to measure the ability of verbal memory function in cognitive impairment are story recall tests and word-list learning tests. However, research is limited regarding which test might be more sensitive in discriminating between normal cognitive aging and patients with Alzheimer's disease (AD) in the Korean population. The purpose of the current study was to compare the word-list learning test (Seoul Verbal Learning Test; SVLT) and the story recall test (Korean Story Recall Test; KSRT) to determine which test is more sensitive in discriminating between individuals with normal cognitive aging and patients with mild cognitive impairment (MCI) and early stage of AD in Korea. A total of 53 healthy adults, 127 patients with MCI, and 72 patients with early stage of AD participated in this study. The receiver-operating characteristic (ROC) curve and area under the curve (AUC) were evaluated to compare these two tests. The results showed that the AUC of the SVLT was significantly larger than the AUC of the KSRT in all three groups (healthy adults vs. MCI and early stage of AD; healthy adults vs. MCI; healthy adults vs. early stage of AD). However, in comparison of patients with MCI and early stage of AD, the AUC of SVLT and the AUC of KSRT were not significant. The word-list learning test is a more useful tool for examining verbal memory function for older adults in Korea than the story recall test.     

The Goteborg MCI study: mild cognitive impairment is a heterogeneous condition

BACKGROUND: Mild cognitive impairment (MCI) has been considered a transitional state between normal aging and dementia, characterised by memory impairment but normal general cognitive functioning. Recently other cognitive deficits have been reported. This has led to a modification of MCI criteria. OBJECTIVE: To examine which neuropsychological tests most clearly distinguish MCI subjects from normal controls. METHODS: 112 consecutive MCI subjects and 35 controls were included in the study. The diagnosis of MCI was based on an objective history of cognitive decline and a neuropsychiatric examination, comprising instruments STEP, I-Flex, MMSE, and CDR. Participants were examined with 21 neuropsychological tests in the cognitive domains speed/attention, memory and learning, visuospatial function, language, and executive function. RESULTS: Controls were significantly older. No differences were found in education or general intellectual capacity. Controls performed significantly better than MCI on tests within all five cognitive domains. The clearest differences were seen on language tests, followed by executive function, and learning and memory. Only two subjects (1.8%) were purely amnestic; 17% showed no impairment compared with controls, with a cut off of 1.5 SD below age mean. These subjects were better educated and performed significantly better on measures of general cognitive capacity. CONCLUSIONS: The results illustrate the heterogeneity of MCI, with a significant degree of impairment in all five cognitive domains. When examined with a comprehensive neuropsychological battery, very few subjects had an isolated memory impairment.     

Neurocognitive testing supports a broader concept of mild cognitive impairment

The narrow concept of mild cognitive impairment (MCI) as an early form of Alzheimer s disease has been broadened by research that established the existence of alternative forms of the condition that may presage other forms of dementia. The research presented here was a naturalistic, cross-sectional study of patients in a community referral clinic-patients with MCI and mild dementia-compared to normal controls. A comprehensive, computerized neurocognitive screening battery developed by one of the authors (CNS Vital Signs) was administered to all of the subjects. Participants consisted of 36 patients with MCI and 53 patients with mild dementia, diagnosed by standard criteria, and 89 matched normal controls. Multivariate analysis indicated significant differences among the three groups for all 15 primary test variables and for all five of the domain scores. Tests of memory, processing speed, and cognitive flexibility were the most cogent discriminators between normal controls and MCI patients, and between MCI patients and patients with mild dementia. The same three tests also had the greatest sensitivity and specificity. The results of this study indicate that computerized testing can differentiate among normal controls, MCI patients, and patients with mild dementia. Also, in a diverse group of MCI and mild dementia patients, impairments in memory, processing speed, and cognitive flexibility were the most prominent observed deficits.     

Japanese version of the Test Your Memory as a screening test in a Japanese memory clinic

A self-administered cognitive test (Test Your Memory, TYM) is designed as a screening test for the detection of Alzheimer disease (AD). We compared the diagnostic utility of the Japanese version of the TYM (TYM-J) in AD and mild cognitive impairment (MCI) with that of the Mini-Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale—Cognitive Subscale Japanese version (ADAS-Jcog). We studied 79 patients with mild AD, 46 with MCI and 34 normal controls. The sensitivity and specificity of each test in the diagnosis of AD and MCI were compared. The average total TYM-J scores were 45.7 in controls, 41.7 in MCI, and 35.7 in AD. The TYM-J scores showed good correlations with other neuropsychological tests. The receiver operating characteristic analysis demonstrated that the TYM-J could better discriminate AD from controls and MCI from controls than the other tests. With each optimal cut-off score of the TYM-J, the sensitivity and specificity were 96% and 91% for diagnosing AD, and 76% and 74% for diagnosing MCI, respectively. The TYM-J is useful for the diagnosis of AD and MCI, and can be applied as a screening test in a Japanese memory clinic.     

CERAD test performances in amnestic mild cognitive impairment and Alzheimer's disease

OBJECTIVES: The aim of the study was to examine the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) test performances cross-sectionally in patients suffering from amnestic mild cognitive impairment (MCI) and mild Alzheimer's disease (AD). Moreover, we wanted to determine the sensitivity to amnestic MCI and mild AD, as well as the specificity of different CERAD subtests in our study groups. MATERIAL AND METHODS: Fifteen healthy elderly individuals, 15 amnestic MCI patients and 15 probable AD patients suffering from mild dementia were tested with the CERAD neurocognitive dementia screening test. RESULTS: Significant differences were found in all CERAD tests except Constructional praxis (copy) and Clock drawing between the controls and the AD group. The MCI group was differentiated from the controls only in the Wordlist learning test. In the language tests the sensitivity to MCI and AD was quite low and the specificity very high. In the savings scores the sensitivity to AD was high, but the specificity rather low. The Wordlist recognition test screened no false positives using the current cut-off score and the sensitivity to AD was 0.6, but only one MCI patient was detected using the current cut-off score. Raising the cut-off score also raised the sensitivity to MCI without dramatic loss of specificity. Cut-off scores for the Wordlist learning test and Wordlist delayed recall, which have been found to differentiate normal aging from dementia, are lacking in the Finnish CERAD. The current data indicates that the Wordlist learning test might be relatively sensitive to MCI. CONCLUSIONS: The results indicate that the Finnish CERAD test battery with its current cut-off scores has low sensitivity to MCI, and using it as a sole cognitive screening instrument for MCI and preclinical dementia might result in false negatives.     

Learning and forgetting new names and objects in MCI and AD

We studied how subjects with mild cognitive impairment (MCI), early Alzheimer's disease (AD) and age-matched controls learned and maintained the names of unfamiliar objects that were trained with or without semantic support (object definitions). Naming performance, phonological cueing, incidental learning of the definitions and recognition of the objects were tested during follow-up. We found that word learning was significantly impaired in MCI and AD patients, whereas forgetting patterns were similar across groups. Semantic support showed a beneficial effect on object name retrieval in the MCI group 8 weeks after training, suggesting that the MCI patients’ preserved semantic memory can compensate for impaired episodic memory. The MCI group performed equally well as the controls in the tasks measuring incidental learning and recognition memory, whereas the AD group showed impairment in this respect. Both the MCI and the AD group benefited less from phonological cueing than the controls. Our findings indicate that word learning is compromised in both MCI and AD, whereas long-term retention of newly learned words is not affected to the same extent. Incidental learning and recognition memory seem to be well preserved in MCI.     

Patterns of verbal memory performance in mild cognitive impairment, Alzheimer disease, and normal aging.

OBJECTIVE: Individuals with mild cognitive impairment (MCI) typically demonstrate memory loss that falls between normal aging (NA) and Alzheimer disease (AD), but little is known about the pattern of memory dysfunction in MCI. METHOD: To explore this issue, California Verbal Learning Test (CVLT) performance was examined across groups of MCI, AD, and NA. RESULTS: MCI subjects displayed a pattern of deficits closely resembling that of AD, characterized by reduced learning, rapid forgetting, increased recency recall, elevated intrusion errors, and poor recognition discriminability with increased false-positives. MCI performance was significantly worse than that of controls and better than that of AD patients across memory indices. Although qualitative analysis of CVLT profiles may be useful in individual cases, discriminant function analysis revealed that delayed recall and total learning were the best aspects of learning/memory on the CVLT in differentiating MCI, AD, and NA. CONCLUSIONS: These findings support the position that amnestic MCI represents an early point of decline on the continuum of AD that is different from normal aging.